Printing processes – Structured surfaces using modern printing technology

Novel additive manufacturing processes are currently being worked on in a variety of research fields. Among the established printing techniques, inkjet printing offers a highly attractive technique for creating surface or three-dimensional structures that are previously designed on the computer.

Digital inkjet printing produces small, uniformly sized droplets that can be used as microcomponents. This allows spatially resolved structures of new, but also known materials to be created in an innovative way. Fraunhofer IGB is therefore focusing its research on inkjet printing as a manufacturing tool for the individualization of production processes.

At Fraunhofer IGB, ink formulations for processing a wide range of functional components such as hydrogels, nanoparticles, proteins and conductive materials are being developed.

• Formulation of aqueous or solvent-based inkjet inks
  
• Biofunctional inks
  
• Inks containing nano- and microparticles
  
• UV curable inks
  
• Conductive and semiconductor inks
  
• Printing of high-resolution structures

To adjust the viscosity and surface tension of functional inks, the properties of the functional components are adjusted. Depending on the requirements, aqueous or solvent-based inks are produced. For applications in tissue engineering, for example, initiator-free cross-linking biocompatible hydrogels are developed and biomolecules are equipped with cross-linkable groups or functionalities through chemical modification to control the solubility properties and viscosity.

For optimal printing results, different substrate materials are pre-treated wet-chemically or by means of plasma technology in order to obtain an optimal print image.

The following examples of inks are in our focus:

• Initiator-free networking two-component systems
  
• Modified biomolecules
  
• Inks containing cells
  
• Suspensions of metallic or oxidic particles
  
• Inks containing carbon

The combination of inkjet printing and the well-known polyurethane chemistry has great potential for future production of functional materials. At present, we are focusing on the production of polyurethane foams using two-component reactive inkjet printing. Two inks (an isocyanate-functional and, for example, a hydroxy-functional ink), each containing a reactive component, are printed separately in layers.